1. Field of the Invention
This invention relates to shelters conforming to the “ICC/NSSA Standard for the Design and Construction of Storm Shelters” (ICC 500), “FEMA Design and Construction Guidance for Community Safe Rooms” (FEMA 361), “ICC International Building Code” (IBC), “ASCE Standard ASCE/SEI 7 Minimum Design Loads for Buildings and Other Structures” (ASCE 7), “AISI Standard North American Specification for the Design of Cold-Formed Steel Structural Members” (AISI S100), and “ACI Standard Building Code Requirements for Structural Concrete (ACI 318)”.
2. Description of Related Art
Tornado shelters are well known and have been built both underground and above ground. The majority of underground tornado shelters are relatively small. Large underground tornado shelters can be built but at significantly higher costs. Underground tornado shelters are not ideal for areas with high level ground water or susceptible to flooding.
Above ground tornado shelters are often defined by a relatively small box or the like constructed out of reinforced concrete, reinforced masonry, thick steel frames and plates, lumber frames covered with thick steel plates or combinations of the above. Larger tornado shelters are commonly made of heavily reinforced concrete. Without intending to be bound by theory, it is believed that the result of the relatively high costs of large concrete tornado shelters is a dearth of community tornado shelters.
It is well known to construct buildings from lengths of rolled steel, each length having been cold-formed into a trough. To assemble such a building, a plurality of arches is constructed, each arch being constructed from a plurality of the lengths, bolted to one another. The arches are upended and bolted to one another, to form an arch building. Hundreds of thousands of ordinary cold-formed steel arch buildings have been constructed. However, these ordinary cold-formed steel arch buildings do not conform to the structural requirements of ICC 500, FEMA 361, IBC, ASCE 7, AISI S100, and ACI 318, especially for 250 mph tornado wind forces, 100 mph 15-lb sawn lumber 2×4 missile impacts, and 100 psf roof live loads.